Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method which remove liquid adhering to various substrates (referred to simply as “substrates” hereinafter) including a semiconductor substrate, a glass substrate for a flat panel display, a substrate for an optical disk, a solar cell panel and the like from the substrates.
Description of the Background Art
In the process steps of manufacturing a semiconductor device, for example, a variety of wet processes using liquid are performed on a substrate, and a drying process is then performed on the substrate subjected to such wet processes. In the process of development in photolithography, a chemical liquid such as a developing solution is applied to a substrate to which a pattern is transferred by exposure to light, and thereafter the substrate is cleaned using a rinsing liquid to remove the chemical liquid from the substrate. The rinsing liquid is replaced with a replacement liquid such as isopropyl alcohol (IPA), and the substrate is dried by removing the replacement liquid.
In recent years, however, there has been a tendency for patterns formed on substrate surfaces to become finer. This gives rise to a problem such that, in the drying process of the replacement liquid, surface tension (or capillary force) acting on a boundary surface between the liquid entering the microstructure of a pattern and a gas in contact with the liquid causes adjacent protruding portions of the pattern to attract each other, thereby collapsing the adjacent protruding portions.
To prevent the collapse of the pattern resulting from such capillary force, there has been a known substrate drying technique using a supercritical fluid. The supercritical fluid is low in viscosity, high in diffusibility, and has no surface tension. There is hence no apprehension that the supercritical fluid brings about the collapse of the pattern when supplied to the substrate. Japanese Patent Application Laid-Open No. 2008-072118 discloses a technique in which carbon dioxide in a supercritical state is supplied to a pattern formed on the surface of a substrate and is then vaporized, whereby the surface of the substrate is dried.
As disclosed in Japanese Patent Application Laid-Open No. 2008-072118, carbon dioxide is relatively easily brought into the supercritical state. However, a high-pressure environment having a pressure as high as 73 atmospheres or more must be set to achieve the supercritical state. Thus, the setting of such an environment in which the supercritical state is achievable necessitates an apparatus for achieving and maintaining a high-pressure state. The provision of such an apparatus requires apparatus costs. These problems become considerations not only in the process of drying the substrate by the removal of the replacement liquid but also in the general processes of removing liquid remaining on the substrate from the substrate.